<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <button id="ldh">刘德华</button>
    <button id="zxy">张学友</button><br>
    <img src="img/刘德华.png" title="刘德华">

    <script>
         // 修改元素属性 src
         // 1. 获取元素
         var ldh = document.getElementById('ldh')
         var zxy = document.getElementById('zxy')
         var img = document.querySelector('img')
         zxy.onclick = function() {
            img.src = "img/张学友.png"
            img.title = "张学友"
        }
        ldh.onclick = function() {
            img.src = "img/刘德华.png"
            img.title = "刘德华"
        }
    </script>
    
</body>
</html>